diff --git a/docs/_config.yml b/docs/_config.yml
index a016d79a..6afaf987 100644
--- a/docs/_config.yml
+++ b/docs/_config.yml
@@ -12,6 +12,14 @@ color_scheme: light
 search_enabled: true
 heading_anchors: true
 
+# Callout styling: `{: .note }` blocks (comments) get a blue left bar,
+# `{: .warning }` blocks get a red left bar.
+callouts:
+  note:
+    color: blue
+  warning:
+    color: red
+
 aux_links:
   "GitHub":
     - "https://github.com/riseproject-dev/python-wheels"